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Clearfield cultivars for 2009

The 2008 season has finally come to end with little avail. Even with the disappointing yields in 2008, many rice farmers are already looking forward with optimism to the 2009 growing season. Clearfield cultivar selection has been a topic of discussion this fall.

Without a doubt, Clearfield rice has had a significant impact on rice production in the Southern rice growing region. It has become the equivalent of “Roundup Ready” soybeans due to its ease of application, and as a result, more rice acres are shifting towards Clearfield. This is something that I am not real enthusiastic about due to potential resistance problems, but it is happening none the less.

To help rice producers make informed decisions on Clearfield cultivars in 2009, “Mississippi Variety Trial” data and information collected in 2008 are summarized below. Only 2008 data is discussed because it is the only data that has “heads up” comparisons of new and standard Clearfield cultivars (Clearfield XL 729, Clearfield XL 746, CL 131, CL 151, CL 161, and CL 171-AR).

Ideally, we would like to have a couple of years of data to make more informed decisions. However, cultivars are now quickly coming to the marketplace and answers are needed.

In 2008, Clearfield XL729 and Clearfield XP 746 showed a 20 to 22 percent yield advantage over CL 161.

CL 151 resulted in an average yield 12 percent higher than CL 161.

Yields with CL 131, CL 161, and CL 171-AR were within a few bushels of each other. Whole rice milling yields of CL 131, CL 161, and CL 171-AR were all above 65 percent and CL 151 averaged 63.3 percent.

Generally, CL 161 always resulted in slightly higher whole milling yields than CL 151.

Clearfield XL 729 and Clearfield XP 746 whole milling yields averaged 59.3 to 59.5 percent.

As with hybrids, whole milling yields are typically lower than varieties.

Plant height for Clearfield XL 729 and Clearfield XP 746 averaged 42.5 inches tall. CL 151, CL 161 and CL 171-AR averaged 38 to 39 inches tall and CL 131 averaged 34 inches tall.

Clearfield XL 729, Clearfield XP 746, CL 151 and CL 161 are all very similar in terms of lodging potential. CL 131 and CL 171-AR have better straw strength over the other cultivars and would therefore offer more resistance to lodging.

Clearfield XL 729 and Clearfield XP 746 have very similar disease resistance packages (moderately susceptible to sheath blight, moderately resistant to blast, moderately resistant to straighthead, and moderately susceptible to kernel smut).

However, in some trials, hybrids that received a fungicide application to prevent/control sheath blight produced higher grain yields. Therefore, it should not be assumed that a fungicide will not be needed with a rice hybrid.

CL 131, CL 151, CL 161, and CL 171-AR are all very susceptible to sheath blight. As a result, these varieties will need at least one fungicide application for sheath blight control.

These varieties rate differently in their susceptibility to blast and straighthead. CL 151 is very susceptible to both blast and straighthead. CL 131 is moderately susceptible to blast and very susceptible to straighthead. CL 161 is susceptible to blast and moderately susceptible to straighthead. CL 171 is both moderately susceptible to both blast and straighthead.

Now, with all this being said, let’s think about cultivar placement and planting strategies. On lighter soils, Clearfield XL 729, Clearfield XP 746, CL 161 and CL 171 would be better suited due to better resistance to blast and straighthead. CL 131 and CL 151 can be grown on lighter soils, but if straighthead is a potential problem, draining will be necessary. Clearfield XL 729, Clearfield XP 746, CL 131 and CL 151 would be well suited on heavier soil.

Since this year’s later planted rice was dismal, most folks have said that they are going to plant until they are done or they can’t plant anymore. With that strategy in mind, we need to plant rice like soybeans, meaning plant the earliest maturing varieties first.

Our recommendation is to plant hybrids first so they can be harvested first. I would then plant in the following order: CL 131, CL 151, CL 161, and then CL 171-AR. Using this strategy will allow you to start harvesting as quickly as possible, and to maximize the quality of your crop.


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